On Tue, Mar 12, 2013 at 10:10 PM, Keith Keller < kkeller@wombat.san-francisco.ca.us> wrote:
On 2013-03-12, SilverTip257 silvertip257@gmail.com wrote:
I've not had any MegaRAID controllers fail, so I can only say they've
been
reliable thus far!
I think that this is not a helpful comment for the OP. He wants to know, in the event the controller does fail, can he replace it with a similar-but-possibly-not-identical controller and have it recognize the
I've had no problem with various versions of Dell MegaRAID/PERC5i controllers. You can swap drives from a PERC5i into a PERC6i for example and things are peachy. But it is not possible to swap drives from a PERC6i into a PERC5i controller.
Avoid SAS6/iR controllers ... they are low-end controllers that only support hardware RAID0 and RAID1.
Ultimately hardware RAID controllers can be a big pain -- just like anything else it's a good business practice to have spares!
original RAID containers. Just because you have not seen any failures so far does not mean the OP never will.
You start by failing/removing the drive via mdadm. Then hot remove the disk from the subsystem (ex: SCSI [0]) and finally physically remove it. Then work in the opposite direction ... hot add (SCSI [1]), clone the partition layout from one drive to the new with sfdisk, and finally add
the
new disk/partitions to your softraid array with mdadm.
You must hot remove the disk from the SCSI subsystem or the block device (ex: /dev/sdc) name is occupied and unavailable for the new disk you put
in
the system. I've used the above procedure many times to repair softraid arrays while keeping systems online.
This is basically the same procedure for replacing a failed drive in a hardware RAID array, except that there is no need to worry about drive
I'll argue that the software RAID process is slightly more complex. And it is crucial that one remember to hot-remove the disk ... after all one could panic their box by just yanking the drive.
I think that information will be useful to the OP and others, so I posted it all. I ought to check the CentOS wiki and see if any/all of those steps are documented.
names (since individual drives don't get assigned a name in the kernel). But the point is that replacing a failed drive is the same amount of on-site work in either scenario, so that should not deter the OP from choosing software RAID. (There may be other factors, such as the aforementioned write cache on many RAID cards.)
--keith
-- kkeller@wombat.san-francisco.ca.us
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